Scientific basis for the Precautionary Principle

The Precautionary Principle is based on two general criteria: (a) appropriate public action should be taken in response to limited, but plausible and credible, evidence of likely and substantial harm; (b) the burden of proof is shifted from demonstrating the presence of risk to demonstrating the absence of risk. Not much has been written about the scientific basis of the precautionary principle, apart from the uncertainty that characterizes epidemiologic research on chronic disease, and the use of surrogate evidence when human evidence cannot be provided. It is proposed in this paper that a new scientific paradigm, based on the theory of evolution, is emerging; this might offer stronger support to the need for precaution in the regulation of environmental risks. Environmental hazards do not consist only in direct attacks to the integrity of DNA or other macromolecules. They can consist in changes that take place already in utero, and that condition disease risks many years later. Also, environmental exposures can act as “stressors”, inducing hypermutability (the mutator phenotype) as an adaptive response. Finally, environmental changes should be evaluated against a background of a not-so-easily modifiable genetic make-up, inherited from a period in which humans were mainly hunters-gatherers and had dietary habits very different from the current ones.